1. Field of the Invention
This invention relates to an apparatus for reading out a radiation image. This invention particularly relates to a radiation image read-out apparatus suitable for detecting a radiation image stored in a stimulable phosphor sheet in a radiation image recording and reproducing system using the stimulable phosphor sheet and for generating an electric image signal. This invention also relates to an apparatus for designating the reproduction processing conditions, i.e. read-out conditions and/or image processing conditions, to an apparatus for reproduction processing of a radiation image, i.e. a radiation image read-out apparatus and/or an image processing apparatus for processing the electric image signal generated by the read-out apparatus.
2. Description of the Prior Art
When certain kinds of phosphors are exposed to a radiation such as X-rays, .alpha.-rays, .beta.-rays, .gamma.-rays, cathode rays or ultraviolet rays, they store a part of the energy of the radiation. Then, when the phosphor which has been exposed to the radiation is exposed to stimulating rays such as visible light, light is emitted by the phosphor in proportion to the stored energy of the radiation. A phosphor exhibiting such properties is referred to as a stimulable phosphor.
As disclosed in U.S. Pat. No. 4,258,264 and Japanese Unexamined Patent Publication No. 56(1981)-11395, it has been proposed to use a stimulable phosphor in a radiation image recording and reproducing system. Specifically, a sheet provided with a layer of the stimulable phosphor (hereinafter referred to as a stimulable phosphor sheet) is first exposed to a radiation passing through an object to have a radiation image stored therein, and is then scanned with stimulating rays such as a laser beam which cause it to emit light in the pattern of the stored image. The light emitted by the stimulable phosphor sheet upon stimulation thereof is photoelectrically detected and converted to an electric image signal, which is processed as desired to reproduce a visible image on a recording medium such as a photographic film or on a display device such as a cathode ray tube (CRT).
In the aforesaid radiation image recording and reproducing system, there is used a radiation image read-out apparatus provided with a read-out means for scanning the stimulable phosphor sheet by stimulating rays and photoelectrically detecting the light emitted by the stimulable phosphor sheet during the scanning to generate an electric image signal.
In many cases, the aforesaid radiation image recording and reproducing system is used for medical diagnosis of the human body or the like. Therefore, the radiation image recording and reproducing system is required to reproduce a visible image suitable for viewing, particularly for diagnostic purposes. In this case, the required quality conditions of the visible image, for example, the output density level, the density level range and the contrast, are different in accordance with the purpose of diagnosis.
Therefore, in order to obtain a more suitable visible image, read-out of the radiation image stored in the stimulable phosphor sheet by use of the read-out means should be conducted by using read-out conditions suitable for the purpose of diagnosis so that an electric image signal which generates a visible image suitable for the diagnostic purpose is obtained.
Also, before the electric image signal generated by the read-out means is used to reproduce a visible image, it is normally subjected to a signal processing such as a gradation processing or a frequency response processing by an image processing means in order to obtain a visible image suitable for diagnostic purpose. In this case also, since the image processing conducted by the image processing means is extremely complicated, the electric image signal should desirably be sent in a pre-processed condition to the image processing means so that the image processing of the type suitable for the particular diagnostic purpose may be achieved easily. Also in order to feed such a pre-processed electric image signal to the image processing means, read-out by the read-out means should be conducted by use of the read-out conditions most suitable for the respective diagnostic purpose